Today, a climate scientist in the U.K. responds to critics of computer modeling. Critics claim that if forecasts of weather just days away are often wrong, how can scientists claim to know what climate will be like 50 years out?
Vicky Pope: We can look at the range of possible outcomes. We’re not saying that there is only one possible future if you do a particular emissions level. We’re saying that there’s a range of possible futures, and that range is representative of the uncertainty in the science.
Vicky Pope is talking about the range of possible risks of climate change. She heads climate change science for the Hadley Centre of the Met Office, the United Kingdom’s national weather service. The Hadley Centre produces some of the world’s most-used climate models. They crunch numbers that simulate the processes that drive Earth’s climate, like incoming sunlight and the circulation and composition of the ocean and atmosphere.
Vicky Pope: The models are based on the laws of physics. So they’re solving the equations that represent those laws. We also run the model every day as a weather forecast. We test it that way. And we compare models of past climate with the observed climate, not just in terms of temperature, but in terms of the physical processes that are important for climate change – like cloud feedbacks, for example.
Dr. Pope said that computer power is the main limitation in simulating in finer detail of climate at a more local scale. She said the long-term models aren’t perfect. Scientists are continually improving them. But these models are the best humanity has for predicting future climate.
EarthSky asked Vicky Pope what she felt was most important for people to know today about climate change.
Vicky Pope: I think it’s important that people understand how much we need to reduce emissions and as quickly as we need to reduce emissions in order to avoid the impacts of dangerous climate change. It’s only if we can peak emissions in the next ten years and reduce at about four percent per year that we’re going to stand a 50-50 chance of limiting temperature rise to two degrees, which would avoid the worst impacts.
Dr. Pope spoke about what she and other scientists see as ‘dangerous’ climate change.
Vicky Pope: The dangerous climate change is different for different people, in different parts of the world. And it’s important that we understand these sort of implications. It’s not a question of reaching a particular threshold and then everything falls apart. It is a gradual change, but we need to be looking out for where does a particular change become irreversible? For example, if the rainforest starts to die, can it recover if temperatures go back down again?
There is also, said Pope, a commitment to climate change from the greenhouse gases, which can persist in the atmosphere for over a hundred years.
Vicky Pope: If we stabilize temperatures to a particular level, it might be that we haven’t started to see any change in that particular aspect of climate or ecosystem. But if we keep the temperature constant, that it continues to change. So again using the Amazon rainforest as an example, at two degrees, we don’t see an impact of climate change. But if we keep the temperature at two degrees, we do start to see an Amazon die-back. That’s an example of commitment. So irreversibility and commitment, I think are really important when looking at dangerous climate change.
Thank you Dr. Pope for responding to critics of climate models. The criticism levied at todays models is well grounded.
It’s not enough to solve equations that represent laws of physics. While the laws don’t change, their effects are modulated by complex interactions. Computer power is a limitation but not the most significant limitation of climate modeling. With incredible computer power, we can get wrong results incredibly fast if we don’t know how to model something accurately.
The real limitation in today’s models is understanding the complex processes that drive climate. The climate is a dynamic system of long term and short term cycles, feedback loops, second and third order processes, step changes, and polynomial cointegration of diverse time series events. Today’s models don’t come close to simulating these processes without a lot of guesstimatons at sensitivities, magic numbers to represent processes not understood, and time series corrections to “adjust” the output to fit observation.
As Willis Eschenbach appropriately said, the current state of climate knowledge is “What we know about the climate, what we know we don’t know about the climate, and what we don’t know we don’t know about the climate.” What we know about the climate is a very small slice of the pie. This is the slice that today’s computer models take into consideration.
To be certain, the models are getting more advanced as we learn those things we know we don’t know. They will be perfected as we discover the things we didn’t know we don’t know. But, as it stands, today’s GCM models have little to no long term predictive skills. I think we need to be more willing to discuss the limitations and uncertainties of today’s models and stop representing them as the reliable and authoritative proof of what the world will be like a decade or 100 years from now.
I think Dr. Pope makes an honest attempt to speak to model limitations and uncertainties but I can’t help but note the dialog then turned to the usual worst case scenarios based presumably on the same models that the MET admits have no long range predictive skills: http://news.bbc.co.uk/2/hi/uk_news/8551416.stm
To Hank
Yes, there is much that we don’t know about the possible ways we can affect the climate. What we do know is that we are pumping massive amounts of emissions of all sorts into the atmosphere. We have three possible scenarios: our activities will have no effect on the climate, a negative effect or a positive effect, whereby I judge whether or not the effects are positive of negative by how they impact the lives of the living things (especially humans) on this planet. We are destroying the rain forests at an alarming rate (again with three possible outcomes) and the same applies to all of the other numerous ways we affect life on the planet (e.g. endangering species through over fishing, deforestation, destroying habitat etc.) It is theoretically possible that we can do all of this without any damage to ourselves, but that is quite unlikely, wouldn’t you say? We still have a lot to learn about what affect we have on life, wouldn’t it be wise to try to slow down our activities which common sense tells us, could be detrimental rather than (as you seem to suggest) continue full speed ahead until we reach the point where we can say with certainty, oh! It would have been better if we had done this or that 10 or 20 years ago?
You sound like the person who is driving full speed on an unknown highway and realizes that he is entering a fog bank. A passenger suggests that there is a possibility that there may be something in the road ahead (a curve, a stopped car, or even animals) to which the driver replies, “we have no way of knowing for sure, so until we have reliable information let’s continue at the same speed.”
A few days ago an asteroid 23′ long missed the Earth by a little over 8000 miles. We had 16 HOURS NOTICE. A volcano is disrupting flight service over Europe. No temperature rise in 10 years. A catastrophic oil leak that no one knows where it is, is going making it non catastrophic. You really need to get it together. And I don’t mean by MAKING UP hockey sticks. Enviromentalism is the new home of Marxists. Climate change is happening. It has for billions of years. Only an elitist can claim to know what is(and has been)happening and blame people for it. You better find a new field to work (?) in because the people are awakening.